Treatment of gold and silver ores



' (No Model.)

' J. H. BURPEIND.

TREATMENT OF GOLD AND SILVER ORES.

No. 587,179. Patente'dJuly 27,1897.

INVENTOR JJL fizzy-fem.

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WITNESSES UNITED STATES PATENT Prion.

JOACHIM H. BURFEIND, OF SALT LAKE CITY, UTAH.

TREATMENT OF GOLD AND SILVER ORES.

SPECIFICATION forming part of Letters Patent No. 587,179, dated July 27, 1897. Application filed July 16, 1896. Serial No. 599,370. (No specimens.)

To all whom it may concern:

Be it known that I, J OACHIM H. BURFEIND,.

sequently precipitated by zinc, besides various quantities of zinc, lime, silica, sulfur, arsenic, mercury, cyanogen, the. The constituents of course vary as the ores from which it is produced vary. Zinc, lime, and cyanogen are always present and frequently constitute fully eighty per cent. of the entire product. The usual method of treating this product is to dry it and then melt it in crucibles with suitable fluxes, which requires a large amount of labor, crucibles, and fluxes, and in melting this impure product there is a great loss of gold and silver through volatilization, and the resulting bullion is seldom over six hundred fine and requires additional refining. Very impure products cannot be treated in this way and are therefore shipped at a great expense to refining-works.

Several methods have been tried for the purpose of reducing the cost of this treatm ent and to avoid the large loss of gold, but as far as I know all have failed. I have discovered that by treating the above-described product with sulfurous acid I can cheaply and quickly remove most impurities, especially zinc, lime, and soluble cyanids, and that the insoluble residue containing the precious metals settles quickly from the salts in solution of the sulfurous acid.

In carrying out my invention I may employ any suitable apparatus.

The accompanying drawing is an elevation, with parts in section, of a plant for producing sulfurous-acid gas and treating the cyanid' product therewith. This drawing illustrates only one way of performing my improved process, and I desire it to be distinctly understood that my invention is not limited to the use of this specific apparatus.

The apparatus shown in the drawing comprises three parts-viz, an air-compressor or air-pump A, a sulfurous-acid generator B, and a vat or other vessel 0, adapted to receive the cyanid product. The air-pump may be of any approved construction, and its delivery-port is connected by means of a pipe D to the bottom of the generator B. Said generator contains an iron pan E, adapted to hold the necessary sulfur. A manhole or hand-hole is provided in the top of the generator or at any other suitable place thereof, said hole being normally closed by a cover F. When it is desired to start the operation, the cover F is removed, so as to enable the attendant to light the sulfur on the pan E. Then the hand-hole is closed and the pump is worked to supply air to the generator. The sulfurous-acid gas thus generated, together with the excess of air, passes out through a lateral opening in the top of the generator and is conveyed through a pipe G to the hollow shaft H of the stirrer H, located in the vat C. A suitable swivel-joint is provided between the pipe G and the shaft H. I is a pulley for rotating the stirrer. Arms J are secured to the lower end of the shaft II, said arms being hollow and communicating with the interior of the shaft. The arms are further perforated, so that the mixture of sulfurousacid gas and air forced into the stirrer by the pump will escape from the arms J in a great number of small jets, thus coming in close contact with the liquid and solid matter in the vat 0.

My method of treatment is as follows: The product above described,either wet and slimy, as it is taken out of the precipitating-boxes, or dry, is put into the vat 0 together with a suitable amount of water. The contents of the said vat, barrel, or other suitable vessel are constantly stirred, and sulfurousacid gas is passed into it in suificient quantity tohave always an excess of the acid in the mixture, which is indicated by the smell. That an excess of sulfurous acid should always be present is an important point, as many salts formedare only soluble in that menstruum, while other salts formed will dissolve some of the precious metals, which is not possible as long as free sulfurousacid is present. After stirring and passing sulfurous-aeid gas into the mixture for, say, ten hours, if one thousand pounds or more of the product are treated, all the contents in the product soluble in sulfurous acid will be dissolved, especially free zine, zine oxid, lime, and also the soluble eyanids. The stirrer is now removed and the mixture is left to settle for about twelve hours. The supernatant liquor can then be drawn off, and the residue, containing all precious metals with some impurities left, is now mixed with strong sulfuric acid and evaporated until heavy fumes of sulfuric acid have come oft for some time. Most impurities insoluble in sulfurous acid are now decomposed. \Vater is now added and the mixture is boiled for a short time, so as to dissolve any anhydrous salts formed. The residue, containing now all the gold and some of the silver with a few insoluble impurities, settles quickly. The supernatant clear solution is drawn off, the residue is dried and melted in the usual way, which can now be done at a minimum cost, and there is no loss of gold and silverin melting except that which is always incurred when remeltin g pure silver and gold. If the method has been carefully manipulated, the bullion obtained will be about nine hundred and fifty fine, but if a finer bullion is wanted ehlorin gas can be passed into the molten metal before it is poured into molds for a few minutes, and the resulting bullion will be nine hundred and ninety to nine hundred and ninety-four fine, requiring no further refining.

Sulfurous acid can be produced from sulfur, pyrites, (be. Pyrites' can usually be bought at very low prices in mining camps, and especially if they carry gold and silver, the residue of them after they have furnished the sulfurous acid will bring such prices as will leave the cost of sulfurous acid next to nothing. By the use of sulfurous acid I have reduced the cost of producing iine gold bars from the above-described product to a few cents per ounce of gold produced, and in particular I avoid the loss of precious metals by volatilization entirely. Local circumstances will be the guides as to the mechanical arrangements,the mode of producing sulfurous acid and the mode of application.

By cyanid product I mean the precipitate or residue obtained by treating the ore with a cyanid solution and subsequently using zinc or its equivalent to precipitate the gold. As hereinbefore explained, said cyanid product contains various other metals besides gold, also impurities in the form of compounds practically insoluble in water. It will be understood that the composition of the above-defined cyanid product may vary considerably, according to the composition of the ore.

Having thus described my invention, I claim as new and desire to secure by Letters Patent- As an improvement in the extraction of precious metals from their ores, the treatment of the cyanid product or precipitate containing said metals, preparatory to melting the said product with sulfurous acid, substantiall y as described.

JOACIIIM ll. BURFEIND.

\Vitnesses:

J. HENRY STUTTEED,

F. RoBERTs. 

